1. Technical Field
This invention relates to the technology of metal cutting and more particularly to reduction of cutting tool wear and vibration in a lubricated metal cutting operation using conventional cutting tool materials.
2. Discussion of the Prior Art
Manufacturing industries, particularly the automotive industry, utilize a significant amount of machining, including turning, drilling, tapping, etc., of aluminum, cast-iron, and steel to fabricate parts, such as cylinder heads, engine blocks, camshafts etc. These machining operations are performed generally using high-speed tool steel or tungsten carbide tools. These tools need to be replaced periodically for wear to maintain dimensional tolerance of parts and also to keep machine vibration under control; such removal results in machine downtime. Therefore, an improvement in tool life would mean less frequent tool replacement resulting in cost savings and reduced machine downtime.
During the past several years some improvement in tool life has been realized through use of more wear resistant materials, such as ceramics or vapor deposited hard coatings, but with higher costs. The present invention provides an alternate route to improve tool life by passing a small direct current through the tool/work-piece interface accompanied by a very little increase in cost but a significant increase in tool wear life. Investigations of the effectiveness of electrical currents, relative to wear elements, have been carried out in a limited capacity by the prior art. In 1969, Ellis and Barrow reported investigating thermally induced electromotive forces in an un-lubricated cutting operation; the electromotive force was augmented with an external circuit (see Annals of CIRP, Vol. XVII, page 39, 1969). The investigators could not confirm a reduction in wear. In 1987 an electrical current was employed to reduce friction in a lubricated bearing contact (i.e. piston and cylinder) by precipitating iron phosphate film from the lubricant (see U.S. Pat. 4,714,529). In 1997, in a wire drawing operation, a DC current was passed between a lubricated capstan sleeve and a copper wire prior to entering a drawing die; water in the lubricant was disassociated to form hydrogen gas which disrupted oxide film formation which allowed easier plastic deformation of pure copper and lower friction in the die (see U.S. Pat. 5,666,839).
None of these prior art approaches teach how to significantly reduce wear in a lubricated metal cutting operation by a reliable and economical technique.
An object of this invention is to provide a method and apparatus that forms an anodic deposit on the tool cutting surface during a lubricated cutting operation, which increases the wear life of the tool and significantly delays the onset of vibration.
The invention, in a first aspect, that meets the above object, is a method of reducing wear in a lubricated metal cutting operation, comprising: (a) providing an electrical cutting cell having an anodic conductive cutting tool and a cathodic conductive work-piece connected to a DC current supply, the lubricant containing platable wear reducing agents and arranged to bathe the contacting interface between the cutting tool and work-piece to function as an electrolyte; (b) controlling the electrical current flow through the contacting interface to be in the range of 25-500 milli-amps; and (c) moving the cutting tool into and along cutting contact with the work-piece while current flows there-between to electro-chemically deposit the wear reducing agents on at least the contacting interface for reducing cutting tool wear and improving ease of mass removal from the workpiece.